Various kinds of techniques about a method for manufacturing silica particles or silica spheres, and a usage thereof have been researched and developed all over the world. Some parts thereof have been already put into practice in bioassays, and others. For the synthesis thereof, TEOS (tetraethylorthosilane, which will be abbreviated to “TEOS” hereinafter) has been conventionally used as a starting material. However, surface layers of particles wherein this material, TEOS, is used are low in chemical reactivity, that is, in bonding capability to foreign proteins or nucleic acids; therefore, an attempt has been made for activating the particles by the introduction of an acceptor group by use of a silica compound different from the material TEOS (Patent Document 1). Known are, for example, the introduction of a SH group by use of MPS (mercaptopropyl ethoxysilane, or 3-mercapto-propyltrimethoxysilane, which will be abbreviated to (MPS)), and that of some other (introduced groups), such as tetraethoxysilane (OH group), or aminopropylethoxysilane (NH2 group). However, these activated silica particles have a double structure composed of an inner shell made of TEOS and an outer shell or surface layer made of an acceptor group, and time, labor and other costs required for the manufacture thereof are high. Moreover, the particles are not easily produced based on the selection of a silica compound wherein the number of bonding sites for forming silica network (Si—O), the number of which is four in TEOS, is three or less (such as MPS). Actually, known is a technique of pre-treating MPS with hydrochloric acid alone (or a mixed liquid of hydrochloric acid and cetylmethylammonium chloride) (at room temperature for 2 to 5 days), adding an aqueous ammonia solution thereto, mixing the components with each other, and further allowing the reactive components to react with each other at room temperature for 2 days, thereby yielding MPS particles (Patent Document 2). However, this technique gives high manufacturing costs, and has complicated manufacturing steps, and further requires considerable days for manufacturing the particles. Additionally, the size (particle diameter) of the manufactured particles is not easily adjusted.
The MPS particles yielded by the method in Patent Document 2 are high in the property that pores have been formed, so that the particles have an advantage that the surface area is enlarged by the formed pores. However, the method is not advantageous in a case where the particles aim for taking in a functional material, or in a case where the particles aim for being used in a quantitative experiment about DNA, a protein or the like. A reason therefor is that as the property that pores have been formed is lower, the number of inner sites where a functional material can be arranged is larger to give a favorable result (a higher fluorescence intensity per particle). Another reason therefor appears to be as follows: about particles having many pores as in Patent Document 2, the effective adhesive area thereof, to which DNA or a protein can adhere, does not depend only on the surface area based on the diameters of the particles, and is varied in accordance with the size or the number of the pores, or the positions thereof; thus, the parameter of the adhesive area is diversified so that a problem is caused for quantitation. Thus, it is required that silica particles having no pores are manufactured.
The present inventors suggest the following in Patent Document 3: silica particles that overcome defects of the conventional silica particles including TEOS particles, that is, high manufacturing costs, low chemical reactivity (bonding capability to foreign proteins or nucleic acids) and other problems, are excellent in functionality and quality and are further able to be mass-produced at low costs; and a manufacturing method thereof. This manufacturing method makes it possible to arrange or incorporate a functional material into surface layers of silica particles or the insides thereof and stabilize the material, thereby allowing the silica particles to have surface layer functionalizing capability or inside functionalizing capability. Examples of the functional material used therein include chemical agents, fluorescent materials, proteins, peptides, nucleotides, nucleotide analogues, oligonucleotides, oligonucleotide analogues and sugar chains; but, the material is not limited thereto. However, in the silica particles invented by the present inventors, the incorporation of a functional material, such as gold colloid or magnetic material, is not conducted. Thus, for the purpose of enlargement of the usage thereof, silica particles having a greater multifunctionality have been desired.
In recent years, the development of biotechnology or nanotechnology has been giving a change to nano medical treatment, imaging or other medical techniques. In conventional imaging, a single probe has been used only in a single estimating method. For example, a magnetic material is used as an imaging agent in an MRI; however, the material is not usually used in any detailed observation with a microscope. However, by technical development in recent years, development of a multifunctional probe having a multimodal function has been desired, and has been advanced, which can be used commonly in vivo and in vitro, or in macro-observation or micro-observation, and further in various machines such as a CT, a PET, and an MRI (Non-Patent Documents 1 and 2). Moreover, a development of multifunctional particles has been desired which give a treatment effect to a multimodal imaging probe and can be used consistently from diagnosis to treatment. Such multifunctional particles would give an innovation to medical treatment and therefore, it is considered that patients' burdens can be relieved, and high treatment effects can be obtained.
However, through the existing imaging agent, macro-observation can be attained, but micro-observation, wherein a microscope is used, cannot be attained. Additionally, a fluorescently labeled antibody used in observation with a microscope cannot be observed through a CT or an MRI. Development competitions of particles having both of a multimodal imaging effect and a treatment effect have been advanced all over the world. However, the particles have a technical problem. Thus, the particles have not yet been completed.    Patent Document 1: WO 2006/070582 Pamphlet    Patent Document 2: WO 2003/002633 Pamphlet    Patent Document 3: Japanese Patent Application No. 2006-160107    Non-Patent Document 1: Journal of America Chemical Society, 2007, 129, 8962-8963    Non-Patent Document 2: Angewandte Chemie International Edition, 2007, 46, 3680-3682